Photographic film



Patentd Feb. 26; 1929.

UNITED STATES PATENT OFFICE.

HAMILTON BRADSI-IAW, OF WILMINGTON, DELAWABE, ASSIGNOB TO E. I. ?DU PONI' DE NEMOURS & COMPANY, OF WILMINGTON, IDELAWAIRE;` A CORPORATION OF' DELAWABE.

rrroroennmc mm.

Application filed March 4, 1927. Serial No. 'zaaa when the film is run through cinematographic apparatus. These charges, if not counteracted, cause markings on the film. The resent`invention has to do with a filnwhic h by virtue of its Construction, overcomes or elimia nates static diflicultes of the character mentioned. The object of this invention is to provide a film having the mentioned and other desirable characteristics.

For several reasons which are well understood, it is desirable 'that the film base or support should he primarily of cellulose nitrate. A difliculty of this material is, however, that it strongly charges electrically, charging negatively. (The gelatine-silver halid emula sion layer charges positively;) In accordance with the present invention there is applied to the back of the film support, i; e. the side opposite that carrying the emulsion, a layer, desirably in the character of a thin hacking, comprising a derivative of cellulose which charges either positively or at least much less negatvely than cellulose nit'ate.

Thus a film is ohtained which, while mainly cellulose nitrate, as is desirable, is yet nonstatic to a substantial de ee. Whether it he made up to he complete y non-static, or but nearly so, will depend, of course, on the desire in any particular case. In particular conformity with the invention, the hacking may desirably comprise a cellulose carhamate, conveni-ently a urethane derivative of cellulose, such as cellulose phenylurethane or cellulose methylurethane.

Without restricting the invention thereto, films emhodying the same are illustrated in the accompanying drawing. In the drawing, the figures are exaggerated conventional cross-sectionalviews, specific description of each fi re being evidently unnecessary in view o the legends thereon.

When carrying a sensitized emulsion, a film exemplifying the present invention preferably comprises a central layer of cellulose nitrate with a sensitized emulsion layer on the one side and a thin layer comprising a celwill develop a lulose urethane on the other. Plainly, the hacking may, if desired, com rise more than one cellulo'sic derivative, so t at the cellulose carbamate may he mixed with other cellulosic wclerivatives such as, for example, cellulose nitrate or acetate.

The general methods of casting a film body and of applying a hacking to it are well known in the art and need not be described here in detail; but as illustrating-the inventon, without however, confining it to the eamples given, the following formulas are gvenz- 1. A dope suitable for casting a film to which emulsion, and hackings of the present invention, may be applied, cellulose nitrate 15 parts by weight, acetone 7 0 parts, camphor v V 2, -ethyl alcohol 10 and amyl alcohol .2 parts.

2. Backing solutions- (a) 1 part cellulose phenylurethane, 19 parts acetone, parts ethyl alcohol. i

(b) l part cellulose phenylurethane, 1 part cellulose acetate, 23 parts acetone and 75 parts ethyl alcohol. i

(a) part cellulose phenylurethane,

part cellulose methylurethane and 24 parts acetone and 7 5 parts ethyl alcohol.

Cellulose nitrate may he used in the hacky ing solutions; for example, in b, a like number of parts of the nitrate may he suhstituted for the acetate, but I prefer the acetate. In Figures 2, 4 and 3 are illustrated films having haokings provided by solutions such as a, b and c, respectively, while Figures 1 and 4 illustrate the use of another cellulose derivative (Fg. 1). e. g. 'the nitrate or acetate (Fig. 4).

All' backings are ap lied as a solution, as will he plain to those s illed in the art (conveniently by means of a roller dipping in a trough) and the solvents evaporated. The hacking layer may be very thin, and it has no efi'ect upon the emulsion when the film is rolled." As indicated, the carhamate used is soluble, to a substantial extent, in desirable solvents. I

The terms positive 'and negative are used to denote that the materials mentioned ositive or negative charge when acted on rictionally. The extent to which the film is completely non-static, depends on various conditions; hut, in any case the employment of layer on the hack sde of the cellulose nitrate, which is either positive' (like the emulsion) or less strongly negative than ordinary cellulose nitrate, e. g. the ce1lulose nitrate 'used as the body layer, is highly advantageous. ln :m broad clams I use "carbamate generical y, to include both unsubstituted and substituted carbamates.

ll claim:

1. A photographic film, including a body layer comprismg a negative material, and a layer comprising a carbamate of cellulose.

2; A photographic film, including a body layer comprising a negative material, and a layer comprising a substituted carbamate oi cellulose.,

3. A photographic film, including a body layer of eellulose nitrate, and a layer comprising a carbamate of cellulose..

l. A photographic film, including a body in which may be hydrogen, an alkyl, or an aromatic, radical.

6. A photographic film comprising a cellulose nitrate body layer carryng on the one side a positive emulsion and on the other side a hacking comprising cellulose phenylcarbamate. I In testimony Whereof I aflix my signature.

HAMILTON BRADSHAW. 

